The present invention relates to a roller bearing and, in particular, to a roller bearing including a plurality of rolling members each of which is formed in a substantially conical shape, a substantially cylindrical shape, or a similar shape.
In a roller bearing including a plurality of substantially cylindrical-shaped or substantially conical-shaped rolling members (which are hereinafter referred to as rollers), if there occurs an axis shift, that is, if the axes of outer and inner races intersect each other, then, in a contact portion between the race surface (so called as an outer racetrack) of the outer race and the rollers and/or a contact portion between the race surface (so called as an inner racetrack) of the inner race and the rollers, on one side of the position where the roller end portions are contacted with the race surfaces of the inner and/or outer races, there may occur locally an increase in the contact pressure (which is hereinafter referred to as edge stress), which raises a fear that the roller bearing may be damaged in the early stage.
Therefore, when mounting the roller bearing onto various devices, it is necessary to make the axes of the outer and inner races coincide with each other with high accuracy, but, in fact, there is a possibility that the axes of the outer and inner races can be shifted/deviated from each other if the rotary shaft of the roller bearing is flexed due to a large axial load.
In order to avoid the above problem, conventionally, there is used a roller bearing in which a crowning operation such as a full crowning operation or a partial crowning operation is performed on the surfaces of the inner and outer races and/or the peripheral surfaces (which are hereinafter referred to as rolling surfaces) of the respective rollers (that is, a conventional roller bearing).
Here, the crowning operation means an operation which works the whole or given areas of buses forming the surfaces of the inner and outer races or the whole or given areas of buses forming the rolling surfaces of the rollers into convex-shaped curved surfaces.
By the way, in the above-mentioned conventional roller bearing, in a large axis shift angle (in which the axes of the outer and inner races can be shifted/deviated from each other by a relatively large angle), in order to prevent the edge stress from occurring between the race surfaces and the rolling surfaces, the radius of curvature of the portion to be crowned must be set small.
However, if the radius of curvature of the portion to be crowned is set small, when the axis shift angle is small (in which the axes of the outer and inner races can be shifted/deviated from each other by a relatively small angle), or when no axis shift occurs, the surface pressures in the central portions of the contact portions between the respective race surfaces and rollers are inconveniently high when compared with a case in which no crowning operation is performed or a case in which the radius of curvature of the portion to be crowned is set large.